lakes stretch back like fiords to the heart of the Cordillera, and are the pride of Patagonia.

The waters of these moisture-laden mountains have, to the east, carved out the Patagonian tableland. It is crossed by broad and boldly cut valleys, several of which, abandoned by the rivers which scoured them, are now dead valleys. The rubbish from the wearing down of the mountains and the glacial moraine has been spread over the whole face of the tableland in the form of beds of gravel. But the rivers that rise in the Andes cross a country of increasing aridity as they descend eastward. There is no tributary to add to their volume. There is none of that softening of lines, of that idle flow of a meandering stream which characterizes the final stage of a river in a moist district. Their inclination remains steep, and their waters continue to plough up coarse sediment; and everywhere, up to the fringes of the valleys, the fluting of the sandstone and steepness of the cliffs bear witness, like the edges of the hamadas of the Sahara, to some other form of erosion than that effected by running water—the influence on the country of the westerly winds. On the tableland the wind polishes the rounded pebbles, makes facets on them, and gives them the colouring of the desert.

Thus from the north to the south of Argentina there is a complete contrast in the way in which the controlling forces of the landscape are distributed. In the north the moist winds come from the east; the rains lessen as they pass westward. The clays, capped with black soil, of Buenos Aires are æolian deposits, brought by the wind from the desolate steppes which close the Pampa to the west, fixed and transformed by the vegetation of a moister region. In the south, on the contrary, the rains come from the Pacific, and the fluvio-glacial alluvial beds of the Patagonian tableland are evidence of copious reserves of moisture in the Andes; but the arid climate in which the waters have left them has made its mark upon their surface.

This diversity of the physical environment is only fully brought out by colonization. It is colonization, the efforts and attempts of human industry to adjust agricultural or pastoral practices to the natural conditions, which enable us to assign the limits of the natural regions. In this differentiation it is essential to notice the historical element.

The introduction of new crops gives a geographical meaning, which had hitherto escaped observation, to climatological limits such, for instance, as the line of 400 millimetres of rainfall which is the western frontier of the region of cereals. These limits of crops remain uncertain for a time, then experience and tradition gradually fix them. They always keep a certain elasticity, however, advancing or receding according as the market for the particular produce is favourable or unfavourable.

Improvement in the methods of exploiting the soil—the adoption of better agricultural machinery, dry farming, etc.—usually leads to the extension of the sphere of a particular type of colonization, as it enables this type to overcome some natural obstacle which restricted its expansion. Sometimes, however, it brings to light a new obstacle and creates a new geographical limit.

To this category belongs the northern limit of the belt of selective breeding, which slants across the plain of the Pampas from the Sierra de Córdoba to the Paraná. The more or less degenerate cattle of the natives had spread over the whole of the South American continent, except the tropical forests, since the seventeenth century, adapting themselves easily to very different climatic conditions, from the Venezuelan llanos to the sertao of Bahía and the plains of Argentina. But pedigree animals, more valuable and more delicate, introduced on to the Pampas fifty years ago, are not able to resist the malady caused by a parasite called the garrapate. Hence the southern limit of the garrapate suddenly became a most important element in the economic life of the Republic. It would lose its importance if we discovered a serum that would give the animals immunity against Texas fever.

The range of one and the same cause varies infinitely with the circumstances. The limit of the prairie, as of the scrub (monte) which surrounds it on every side, and keeps it at a distance of 320 to 440 miles from Buenos Aires, had no decisive influence on primitive colonization. Whether covered with grasses or brushwood, the plain is equally suitable for extensive breeding. The ranches are the same on both sides of the border. At the end of the nineteenth century, however, when the area of cultivation increased, the prairie was at once found to be superior. The labour required for clearing the brushwood before the plough can work is enough to divert from it, at least for some time, the stream of agricultural colonization. While the population of the monte, wood-cutters and breeders, are indigenous, the prairie has absorbed the immigrants from Europe, and the border of the scrub has become in many places an ethnographical frontier.2

THE ARID ANDES. PUNTA VACAS, ON THE TRANS-ANDEAN RAILWAY.

The bottom of the valley is 8,000 feet above sea-level; the sides buried under rubbish. It is especially in this latitude, above a height of 10,600 feet, in the zone where the moisture falls as snow even in summer, that the rock is everywhere buried under its own rubbish. This is Keidel's Schuttzone. It extends to the foot of the Alpine peaks, carved by glaciers.

Photograph by Moody, Buenos Aires.

Click to view larger image.